The present invention is directed generally to a waterbed mattress including a spring insert for auxiliary support for loads placed on the mattress above the insert.
Improved sleep is experienced on a waterbed mattress, compared to sleep on a conventional mattress, because the support forces are more uniformly distributed across the body thereby substantially eliminating localized pressure points. This same characteristic, however, makes the top surface of a waterbed mattress more susceptible to deflection by a concentrated load such as when one sits or kneels on a waterbed mattress. Internal baffling systems and foam and fiber fillers have been incorporated into waterbed mattresses to eliminate wave action and restrict the flow therein. These, however, have only indirectly improved the resistance of a waterbed mattress surface to deflection by a concentrated load.
Previous attempts have been made to incorporate springs within a waterbed mattress. Callaway U.S. Pat. No. 4,245,363, for example, provides coil springs within an annular chamber surrounding a central waterbed mattress bladder to support one seated on the edge of a waterbed mattress. An alternate embodiment shows coil springs within the waterbed mattress bladder as well. Such a mattress, however, requires structure for supporting the individual coils and for preventing puncture of the mattress walls, all of which increase the expense of the mattress. The complexity inherently presents manufacturing problems and an increased number of potential failure points on the mattress.
Accordingly, a primary object of the invention is to provide an improved spring insert for a waterbed mattress.
Another object is to provide such an insert which includes a plurality of spring bellows units.
Another object is to provide such a spring insert which does not require mechanical attachment to the waterbed mattress.
Another object is to provide such a spring insert which combines mechanical spring resistance with flow resisting chambers to effect shock absorption as well as spring resistance to concentrated loads on a waterbed mattress.
Another object is to provide a spring insert in which a plurality of spring units are arranged and supported relative to one another.
Another object is to provide such a spring insert which is free of attachment to the bottom wall of the mattress but which functions substantially as if it were so attached.
Another object is to provide such a spring insert wherein the spring bellows units are arranged in a nonuniform distribution to impart different support for different areas of the mattress top wall.
Another object is to provide such an insert wherein the spring bellows units have different force/deflection characteristics to likewise vary the degree of support at different positions on the waterbed mattress.
Another object is to provide such a spring insert wherein certain spring bellows units have different heights and cross sectional areas to further vary the degree of support by the different bellows units.
Another object is to provide such a spring insert wherein the bellows units are provided with valved bleeder openings.
Another object is to provide such a spring insert wherein the bellows units are enclosed within flexible covers defining secondary hydraulic chambers between the bellows units and respective covers.
Another object is to provide such a spring insert wherein joint hydraulic chambers are formed by stacked pairs of upper and lower bellows units.
Another object is to provide such a spring insert with a valve for adjusting fluid communication between stacked pairs of upper and lower bellows units.
Another object is to provide such a spring insert with channels between adjacent spring bellows units for limited fluid communication between them.
Another object is to provide an improved waterbed mattress including the spring insert of the invention.
Another object is to provide such an improved waterbed mattress and spring insert which are simple and rugged in construction, economical to manufacture and efficient in operation.